1. Field of the Invention
The present invention relates to a space diversity receiver for use in a radio transmission system, and more particularly to a space diversity receiver with an improved signal-to-noise ratio feature and a method thereof.
2. Description of the Related Art
In general, a space diversity receiver for use in a radio transmission system combines signals received from two or more antennas and provides a receiver with the combined signal to minimize fading and distortion due to environmental conditions. To get the combined signal from two antennas it is known to use the signal strength of the two signals, the amplitude to frequency signal dispersion, or the phase difference between the two signals to decide whether to combine the received signals.
It is known that the typical space diversity receiver signal combiner is positioned at a front stage of an intermediate frequency amplifier in the radio transmission system, and the intermediate frequency amplifier may compensate the signal generated from the signal combiner. However, when the signal combiner is placed in a rear stage of the intermediate frequency amplifier, like the system to which the present invention is applicable, the signal output from the signal combiner may not be compensated.
U.S. Pat. No. 5,530,925 to Charles L. Garner entitled Intermediate Frequency Combiner For A Radio Communication System contemplates a system in which the decision on whether or not to combine two intermediate frequency signals, received from diverse antennas, is based on signal strength of the two signals and the amplitude to frequency signal dispersion. Additionally, a phase detector/corrector is provided to compensate for the phase difference between the two signals prior to squelching one of the signals in response to the received signal strength and signal dispersion.